The present invention relates to an improved generator and fan. More specifically, the invention provides a generator utilizing an improved rotor fan.
Without a generator, the electrical load of a vehicle would quickly drain a fully charged battery. In a vehicle, a generator producing alternating current (AC), known as an alternator, is often mounted at the front of the engine and is linked to the engine crankshaft pulley by a drive belt. When the engine turns the drive belt, the drive belt turns a shaft in the alternator, and current is generated. Current is produced in an alternator when a wire intercepts a magnetic field. In an alternator, it is the wire, in coiled form, that is held stationary and the magnetic field is turned so that the magnetic field passes through the wire. Thus, alternators include a stationary part, the stator, and a rotating part, the rotor.
The stator may include stationary coils or slotted pins or segments that surround a rotor. As the rotor is turned by the car engine, the alternating magnetic field created by the rotor is intercepted by the stationary coils, pins or segments, and current flows through the stator first in one direction, then in the other, resulting in alternating current. As the rotor is turned, air flow within the assembly will produce noise in the audible range that will emanate from the alternator assembly.
The rotor includes an electromagnet that is magnetized by current from the battery. The electromagnet may include slip rings, rotor windings, and north and south pole members surrounding the rotor windings. Current from the battery flows through the slip rings to the rotor windings. North and south pole members have pole claws shaped like interlocking teeth surrounding the rotor windings. The north and south pole members create an alternating magnetic field as the rotor turns.
A housing surrounds the rotor and stator assembly. The stator is fixed relative to the housing and the rotor shaft is rotatably mounted relative to the housing. Because the battery and electrical components in the car work on direct current (DC), the AC output of the alternator must be converted to DC. This is done with rectifiers which pass current in one direction only. The components within the alternator produce heat and, in addition, the alternator operates under high under hood temperatures. To reduce the amount of heat in the alternator, a fan is included in the alternator assembly as seen in reference to U.S. Pat. No. 4,549,103 to Shega, entitled Multi-Path Cooling in an AC Generator for a Vehicle.
The fan may be placed inside or outside of the housing to increase airflow between the rotor and stator and to increase airflow through openings in the housing. The fan blades may face inward toward the central portion of the alternator or outward away from the central portion of the alternator. Rotation of the fan helps increase airflow within the alternator and helps to reduce heat within the alternator, but also increases the amount of audible noise emanating from the alternator assembly, an undesirable feature particularly from the point of view of the operator of the vehicle in which the alternator is mounted.
The noise produced by an alternator depends, at least in part, on the design of the alternator fan blades. Alternator fans with straight fan blades having an inside angle of more than ninety degrees from the base of the fan, tend to produce less noise, but undesirably also provide less airflow. Alternator fans with straight fan blades at ninety degrees from the base of the fan produce more airflow, but undesirably more noise. To improve the airflow resulting from a fan with swept out blades, the length of the blade can be increased but this undesirably reduces the number of blades that can be included on a single fan. Other designs have incorporated alternating blades, some blades at ninety degrees and other blades having an inside angle of more than ninety degrees. However, the limitations associated with each type of blade are not entirely overcome by known designs. The present invention overcomes these problems to provide an alternator incorporating an improved fan, resulting in an alternator with reduced noise, improved tonality and improved radial and axial cooling airflow.
The present invention provides an improved generator with improved sound quality and reduced noise level, and also provides improved airflow through the generator, improving cooling of the generator components. An improved generator fan serves to draw air into the generator through an inlet in the generator housing, pass the air through the rotor and stator, and direct the air out openings in the generator housing. The fan of the present invention includes a disc adapted to be centrally mounted on a shaft that represents an axis about which the fan rotates.
According to the present invention, at least one multi-directional blade extends from the disc. The multi-direction blade includes a leading segment extending from the disc between a first radius measured from the axis of rotation and a second radius measured from the axis of rotation, the leading segment including a leading edge extending from the disc at an angle of about ninety degrees from the disc, the leading segment extending from the disc with a swept out shape starting at the leading edge and extending from the disc with an increasing angle along the length of the leading segment. A trailing segment extends from the disc between the second radius and a third radius measured from the axis of rotation, the third radius being greater than the second radius and the trailing segment extending from the disc with an angle having a rate of change different than the leading segment.
An improved generator having the inventive fan exhibits improved tonality and a reduced noise level. The resulting generator also provides improved cooling. Other aspects of the present invention are provided with reference to the figures and detailed description of embodiments provided herein.